The present invention relates generally to a motor main shaft, and more particularly to a cooling means of the motor main shaft.
The main shaft in high-speed motion generates a great deal of heat power resulting from the motion of a motor, the pre-compression friction of the bearings, and the heat stress caused by the uneven heat expansion of the bearings and the spacing rings. In light of the heat power, the head of the main shaft is apt to sway or expand. Such a deficiency may be overcome by enlarging the pre-compression value of the bearings. However, such remedy often results in the burnout of the bearings.
The conventional cooling means include refrigerator, coolants, variable pre-compression mechanism, and lubricant. The use of refrigerator is not only costly but also ineffective in view of the fact that the main shaft must be provided with a water jacket, and that the temperature and the quality of the cooling water can not be controlled with ease and precision, and further that the cooling is only superficially effective. The use of coolants requires the structural redesign of the main shaft such that a compressor or pump is called for. The application of a variable precompression mechanism is not cost-effective, due to the design complication of the mechanism. The lubricant is intended to reduce the mechanical friction to a limited extent and must be therefore used in conjunction with a cooling system.
The primary objective of the present invention is to provide a main shaft with a cooling means capable of cooling effectively and economically the main shaft in motion.
In keeping with the principle of the present invention, the foregoing objective of the present invention is attained by a main shaft which is provided with a plurality of bearings fitted thereover at an interval, and a plurality of spacing rings fitted thereover such that each of the spacing rings is located between two bearings. The spacing rings are provided with a plurality of cooling fins. The main shaft is further provided with a sleeve which is fitted over the bearings and the spacing rings.